Question

An object of weight 1 N is falling vertically. The time vs. speed data can be found
here. In this case the effect of air-drag cannot be neglected. Use your critical thinking to estimate
the air-drag coefficient . Make sure you include the units in your answer.

0   0
0.1   0.9992
0.2   1.993
0.3   2.978
0.4   3.948
0.5   4.898
0.6   5.826
0.7   6.728
0.8   7.599
0.9   8.438
1   9.242
1.1   10.01
1.2   10.74
1.3   11.43
1.4   12.09
1.5   12.7
1.6   13.28
1.7   13.82
1.8   14.33
1.9   14.8
2   15.23
2.1   15.64
2.2   16.01
2.3   16.36
2.4   16.67
2.5   16.97
2.6   17.23
2.7   17.48
2.8   17.71
2.9   17.91
3   18.1
3.1   18.28
3.2   18.43
3.3   18.58
3.4   18.71
3.5   18.83
3.6   18.94
3.7   19.03
3.8   19.12
3.9   19.21
4   19.28
4.1   19.35
4.2   19.41
4.3   19.46
4.4   19.51
4.5   19.56
4.6   19.6
4.7   19.64
4.8   19.67
4.9   19.7
5   19.73
5.1   19.76
5.2   19.78
5.3   19.8
5.4   19.82
5.5   19.84
5.6   19.85
5.7   19.87
5.8   19.88
5.9   19.89
6   19.9
6.1   19.91
6.2   19.92
6.3   19.93
6.4   19.93
6.5   19.94
6.6   19.95
6.7   19.95
6.8   19.96
6.9   19.96
7   19.96
7.1   19.97
7.2   19.97
7.3   19.97
7.4   19.98
7.5   19.98
7.6   19.98
7.7   19.98
7.8   19.98
7.9   19.99
8   19.99
8.1   19.99
8.2   19.99
8.3   19.99
8.4   19.99
8.5   19.99
8.6   19.99
8.7   19.99
8.8   19.99
8.9   19.99
9   20
9.1   20
9.2   20
9.3   20
9.4   20
9.5   20
9.6   20
9.7   20
9.8   20
9.9   20
10   20

Answer 1

v vst The figure on the right shows the speed as function of time, the terminal speed is 20 m/s When the object moves at this speed, the net acceleration is zero, so the net force is zero, then: Fnet = mg - fr = 0 mg – kv = 0 The air-drag coefficient| , mg 1 k = = 2 = 0.05 NS 20 40 60 80 100 120